Beber vs. beberse
This article explains the difference between the Spanish words 'beber' and 'beberse', both of which mean 'to drink'.
Beber
'Beber' is a general verb meaning 'to drink'. It describes the action of drinking without emphasis on consuming the entirety of the liquid.
Quiero beber agua.
(I want to drink water.)
Voy a beber un poco de jugo.
(I am going to drink some juice.)
Ellos suelen beber café por la mañana.
(They usually drink coffee in the morning.)
¿Quieres beber algo?
(Do you want to drink something?)
Beberse
'Beberse' is a reflexive verb meaning 'to drink up' or 'to drink entirely'. It emphasizes that the person drinks every last drop of the liquid.
Ella se bebió toda la leche.
(She drank up all the milk.)
Nos bebimos el vino en la fiesta.
(We drank up the wine at the party.)
Él se bebió el jugo en un solo trago.
(He drank up the juice in one gulp.)
Me bebí el agua después de correr.
(I drank up the water after running.)
Summary
In summary, while 'beber' refers to drinking without necessarily finishing everything, 'beberse' emphasises drinking everything until it's gone. The examples make it clear that 'beber' is used for drinking in general, whereas 'beberse' is used when someone has drunk all of the liquid completely.